Currently, the stereoscopic display technologies are rapidly developed. The stereoscopic display technology forms a stereoscopic impression using the binocular parallax. The main stereoscopic display technology adopts the spectacles mode which is more mature and more economical than the naked-eye mode. The stereoscopic display of spectacles mode further includes red interconvert blue mode, shutter mode and polarized light mode that enable the left and right eyes to receive different pictures in different manners (wavelength, time and polarization difference). Reference is made to FIG. 1 which is a stereo virtual image produced by extending the images in an opposite direction until the images overlap, the images based on matter of people's left and right eyes saw. It can be seen from FIG. 1 that the distance from the virtual image to the display screen is not fixed but is proportional to the distance between the human eyes and the display screen. Thus, the location of the stereo virtual image also moves following the movement of the head of the user but is not changeless; therefore, a problem of irreal stereoscopic impression is brought to the user.
In the prior art, the automatic tracking technology is used in most cases in order to reduce the irreal stereoscopic impression of the stereo virtual image due to change of the user's location. For instance, in the invention for a patent of the application No. 02803042.7 and publication No. CN1476730A, entitled Autostereoscopic Image Display with Observer Tracking System, the apparatus uses a viewpoint tracker to control the slits of the parallax barrier to vary the incidence of light beams into the lenses to effect the angle of refraction within the lenses causing the outgoing lightbeams carrying pixels of the right and left eye views to converge into at least one distinct right and one distinct left eye view focus, respectively, coinciding with the eye positions of said observers, so as to reduce the irreal impression of the stereo virtual image due to change of the user position. Samsung discloses in the invention for a patent of the application No. 200710180225.X, entitled Method for Adjusting Disparity in Three-dimensional Image and Three-dimensional Imaging Device thereof, which uses a parallax estimator and a parallax adjustor to adjust the image by estimating the parallax so as to provide an optimal stereoscopic effect to the user.
Though the solutions in the prior art reduce the problem of irreal stereoscopic impression of the stereo virtual image due to change of the user's location, they are obviously not sufficient to maintain a real stereoscopic impression of the virtual image.